I/O JMAP

JMAP client library for Rust

This library is composed of 3 feature-gated layers:

• Low-level I/O-free coroutines: no_std-compatible state machines containing the whole JMAP logic, usable anywhere
• Mid-level light client: a standard, blocking client wrapping a stream you opened yourself
• High-level full client: the light client plus TCP connections and TLS negotiations handled for you

Table of contents

• Features
• RFC coverage
• Usage
• Examples
• AI disclosure
• License
• Social
• Contributing
• Sponsoring

Features

• Session discovery: resolves the JMAP session from a base URL or the well-known endpoint, surfacing redirects to the caller instead of following them.
• Core protocol: batched method calls, generic get, set, query and changes flows, blob upload and download.
• Push notifications: push subscription management and the streaming Event Source channel, yielding one state change per push frame with cooperative shutdown.
• Mail: mailboxes, emails, threads, identities, email submissions and vacation responses.
• Contacts: address books and contact cards, the JSContact payload kept as raw JSON.
• Full standard, blocking client with TLS support:
  • Rustls with ring crypto (requires rustls-ring feature, enabled by default)
  • Rustls with aws crypto (requires rustls-aws feature)
  • Native TLS (requires native-tls feature)

[!TIP] I/O JMAP is written in Rust and uses cargo features to gate the client layers. The default feature set is declared in Cargo.toml or on docs.rs.

RFC coverage

Usage

The whole API is documented on docs.rs, including runnable snippets for every coroutine and client.

Examples

Complete runnable programs live in ./examples; the tests also demonstrate real usage against live JMAP servers.

AI disclosure

This project is developed with AI assistance. This section documents how, so users and downstream packagers can make informed decisions.

• Tools: Claude Code (Anthropic), invoked locally with a persistent project-scoped memory and a small set of repo-specific rules.
• Used for: Refactors, mechanical multi-file edits, boilerplate (feature gates, error enums, derive macros, trait impls), test scaffolding, doc polish, exploratory design conversations.
• Not used for: Engineering, critical code, git manipulation (commit, merge, rebase…), real-world tests.
• Verification: Every AI-assisted change is read, compiled, tested, and formatted before commit. Behavioural correctness is verified against the relevant RFC or upstream spec, not assumed from the model output. Tests are never adjusted to fit AI-generated code; the code is adjusted to fit correct behaviour.
• Limitations: AI models occasionally produce code that compiles and passes tests but is subtly wrong. The verification workflow catches most of this; it does not catch all of it. Bug reports are welcome and taken seriously.
• Last reviewed: 15/07/2026

License

This project is licensed under either of:

• MIT license
• Apache License, Version 2.0

at your option.

Social

• Chat on Matrix
• News on Mastodon or RSS
• Mail at pimalaya.org@posteo.net

Contributing

Contributions are welcome: start with CONTRIBUTING.md, which opens with the Pimalaya-wide guides to read first.

Sponsoring

Special thanks to the NLnet foundation and the European Commission that have been financially supporting the project for years:

• 2022 → 2023: NGI Assure
• 2023 → 2024: NGI Zero Entrust
• 2024 → 2026: NGI Zero Core
• 2027 in preparation…

If you appreciate the project, feel free to donate using one of the following providers: